Various measures for reduction of emissions of carbon dioxide (CO2) are being taken in order to deal with atmospheric pollution and global warming. In particular, in the automobile industry, the reduction of emissions of CO2 is highly expected in association with the spread of electric vehicles and hybrid electric vehicles. Thus, development of high-performance secondary batteries serving as driving power sources of motors for use in such vehicles, is actively being carried out.
For the secondary batteries serving as driving power sources of motors, a higher capacity and cycle property are particularly required. Thus, lithium ion secondary batteries having high theoretical energy are gaining increased attention among other types of secondary batteries. The lithium ion secondary batteries are required to store a large amount of electricity per unit mass in positive electrodes and negative electrodes, in order to increase energy density of the lithium ion secondary batteries. Therefore, the determination of active materials used in the respective electrodes is quite important so as to fulfill such a requirement.
There are known methods for manufacturing electrode materials used for lithium ion secondary batteries having a high discharge capacity per volume and a high charge-discharge cycle property (for example, refer to Patent Literature 1). In particular, Patent Literature 1 discloses a method for manufacturing an electrode material including composite particles having a predetermine average particle diameter and specific surface area obtained in a manner such that fine particles mainly including silicon, metal powder including predetermined elements such as tin and aluminum, and carbon powder are dry-milled. Patent Literature 1 also discloses that such an electrode thus obtained is used for a negative electrode for a lithium ion secondary battery.